In the case of such devices the piezoresistive pressure sensor is provided in order to obtain the maximum degree of integration on a semiconductor substrate. The piezoresistors serve as transducers, the piezoresistive effect being relied upon in order to obtain an electrical signal representative of the pressure present in a measuring system.
A condition for the desired linear pressure to voltage transfer function is not only a minimum flexure of the membrane, but furthermore more particularly an accurate positioning of the piezoresistors. The same should as far as possible be provided in regions, in which the membrane has its maximum stress field. The position of these regions on the outer side of the epitaxy layer is however dependent on the position of the part of the epitaxy layer constituting such membrane, such part being determined by the opening etched free from the rear side. What is controlling here is the region of the opening directly adjacent to the epitaxy layer, since it defines the edge of the membrane.
This opening region which is responsible for defining the membrane is however not dependent on the particularities of electrochemical anisotropic semiconductor etching, but furthermore and more particularly on the respective positioning of the rear side mask and the thickness of the semiconductor substrate. Since both the positioning of the rear side mask in relation to the front side of the semiconductor device and furthermore the thickness of the wafer are always subject to certain fluctuations, the desired linearity of the transfer function is not attained in every case; The reproducibility of linear piezoresistive pressure sensors is therefore impaired by certain production parameters.
On the other hand, one object of the invention is to provide such a further development of the semiconductor device of the type initially mentioned and of the method for the production thereof. In the latter sense, the simplest possible means for optimum reproducibility of the linear transfer function of the piezoresistive pressure sensor which may be obtained practically independently from the respective positioning of the rear side mask is employed.